Hybridization and introgression in Carex aquatilis and C. paleacea

Abstract

The genetic relationships among the sedges Carex aquatilis, C. paleacea, and C. recta, and C. recta and other hybrids (C. aquatilis × recta and C. paleacea × recta) were investigated. Microsatellite-based, dominant inter simple sequence repeat (ISSR) fingerprinting revealed no taxon-specific variation among five investigated Carex species or hybrids, while in codominant microsatellite genotyping, 5 out of 16 alleles were taxon specific. Despite significant genetic differentiation, our results demonstrate that there is also gene flow between taxa. Although principal component analysis (PCA) showed some structuring among groups, there was considerable overlapping. The analysis of genetic differentiation assessed for the expected five groups using the program Structure did not provide conclusive results for the number of main groups. However, it is visible that C. aquatilis and C. paleacea are genetically distinct, while the other studied taxa show intermediate genetic features. Both the microsatellite analysis and sequencing of the internal transcribed spacer (ITS) region supported the view that the parental species of C. recta are C. aquatilis and C. paleacea, although with unequal contribution. C. paleacea × recta is likely to possess additional genetic material apart from that originating from C. aquatilis and C. paleacea. Our study shows that ISSR markers failed to be sufficiently informative, but the combination of sequencing (ITS) and the use of microsatellite genotyping proved their applicability in resolving fine-scale taxonomic questions.